Cooling device for electric equipment

ABSTRACT

A cooling device for an electric equipment which is excellent in cooling efficiency and low in noise and permits easy mounting of a cooling fan and a fan guard, comprising a heat sink ( 1 ) having a U-shaped frame ( 4 ) consisting of a flat part ( 2 ) and side parts ( 3 ) disposed on the opposite sides of the flat part ( 2 ), fins ( 5 ) formed on the frame ( 4 ) and fan guard mounting holes ( 6 ) formed in the side parts ( 3 ) of the frame ( 4 ); a cooling fan ( 7 ) having an engaging recess ( 8 ) in the side thereof; and a U-shaped fan guard ( 9 ) consisting of a fan guard body ( 10 ) and side plates ( 11 ) disposed on the opposite ends of the fan guard body ( 10 ); wherein a lattice body ( 12 ) is provided on the fan guard body ( 10 ), an air guide ( 17 ) at the tip end of each side plate ( 11 ), a fan mounting engaging projection ( 13 ) on the inner side surface of each side plate for clamping and retaining by engaging the cooling fan ( 7 ) and a projection support ( 15 ), having an engaging projection ( 14 ) for mounting the fan guard ( 9 ) to the heat sink ( 1 ), on the outer side surface of each side plate.

TECHNICAL FIELD

The present invention relates to a cooling apparatus for electricalequipment employed in, for example, control units such as inverters.

BACKGROUND ART

FIGS. 3 and 4 show a typical conventional cooling apparatus forelectrical equipment.

In these drawings, the reference number 21 indicates a heat sink of acontrol unit (not shown) such as an inverter. The heat sink 21 comprisesa gate-shaped frame 24 having a flat section 22, with side sections 23located respectively on both sides of the flat section 22, and fins 25.The frame 24 of the heat sink 21 is equipped with an electronic device(not shown) and thermally connected to a heating member. A cooling fan26 is to be mounted to the frame 24 of the heat sink 21, and a fan guard27 is to be mounted to the cooling fan 26 so as to cover the front faceof the cooling fan 26 with a grille section 28 of the fan guard 27. Thecooling fan 26 and fan guard 27 are formed with through holes 29 and 30provided in corresponding positions, respectively. A long clamping screw31 is respectively put through these through holes 29 and 30, and thenscrewed into a corresponding threaded hole (not shown) formed in theframe 24 of the heat sink 21 to fasten the cooling fan 26 and fan guard27 to the heat sink 21.

The above-mentioned construction is cooled by the following manner.

A cooling airflow generated by driving the cooling fan 26 is directedinto the interior of the frame of the heat sink 21. The cooling air ispassed between fins 25 of the heat sink 21 and discharged to outside ofthe control unit and others. When the cooling air is passed between fins25, heat exchange is performed between the fins 25 and the cooling airso that the heat sink 21, absorbing heat from the electronic device andothers (not shown) drops in temperature. Thus, the electrical equipmentincluding the control unit is cooled.

However, in the conventional cooling apparatus for electrical equipment,the following problems have been recognized.

(1) Inefficiency in utilizing the cooling air due to the circumventionof the cooling air through a side space of the cooling fan 26.

As shown in FIG. 4( a), when the cooling airflow generated by thecooling fan 26 flows between the fins 25 of the heat sink 21, a part ofthe cooling air comes in conflict with the front end of the fins 25 ofthe heat sink 21 so that a turbulence is caused in the cooling airflow.

In addition, between the cooling fan 26 and the heat sink 21, thereexists a gap formed over the entire surface of the cooling fan 26 in itswidth direction at approximately the same position in the longitudinaldirection of the cooling fan 26. Thus, the turbulent cooling air yieldsa kinetic energy in the width direction on the cooling fan 26, and caneasily escape from the gap between the cooling fan 26 and the fins 25through a side space of the cooling fan 26. Then, as shown by the arrowin FIG. 4( a), the cooling air escaping from the gap is turned over toan inlet port of the cooling fan 26, which results in inefficiency inutilizing the cooling air.

(2) Inefficiency in cooling due to high air resistance in the grillesection 28 of the fan guard 27. Undesirable wind noise occurs in thegrille section 28.

As shown in FIG. 4( b), the generated cooling airflow is directed on atilt in the rotation direction of the cooling fan 26 with respect to arotation axis of the cooling fan 26. Thus, when the cooling air issucked toward the cooling fan 26, the cooling air obliquely passesthrough the grille section 28 of the fan guard 27 so that the airresistance of the grille section 28 is increased and the substantialairflow area of the grille section 28 is decreased, resulting in loweredefficiency in cooling. Further, each corner of the grille section 28protrudes into the path of the cooling air so that the corner createsair turbulence to cause undesirable wind noise.

(3) Low efficiency and difficult assembly due to the fastening structurein which the cooling fan 26 and the fan guard 27 are commonly clamped tothe heat sink 21 by the clamping screw 31.

As shown in FIG. 3, the cooling fan 26 and the fan guard 27 are commonlyclamped and fastened to the heat sink 21 by the long clamping screw 31.Thus, the positioning of individual parts and the clamping of theclamping screw 31 are required to simultaneously operate, resulting inlow efficiency and difficult assembly.

As a result, the effort required for periodical maintenance check andreplacements for the cooling fan 26 inevitably deteriorates operationalefficiency.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a cooling apparatusfor electrical equipment, which has excellent cooling efficiency and lownoise and is easily assembled with a cooling fan and a fan guard.

In order to solve the aforementioned problems, a cooling apparatus forelectrical equipment according to the present invention, comprising: aheat sink including a gate-shaped frame having a flat section and sidesections located respectively on both sides of the flat section, finsformed on the frame, and a fan guard mounting hole formed in the sidesection of the frame; a cooling fan having an engaging groove in each ofside sections of the cooling fan; and a gate-shaped fan guard includinga fan guard body and side plates located respectively on both sides ofthe fan guard body, wherein the fan guard body includes a grillesection, the side plates including a shroud section at the rear endportion of each side plate, the side plates being provided with a fanmounting/engaging protrusion for pressingly clamping and engaginglyretaining the cooling fan, on the inner surface of the side plate, theside plates including a protrusion supporting section having an engagingprotrusion for mounting the fan guard to the heat sink, on the outersurface of each side plate.

Thus, cooling air is guided to the heat sink by the shrouded section ofthe fan guard to create a smooth cooling airflow, so that coolingefficiency can be enhanced. Further, the fan and the fan guard as wellas the fan guard and the heat sink can be fastened to each other by theengaging portions provided in the fan guard in a snap-in manner, so thatthe cooling fan and the fan guard can be easily assembled, or mountedto, and disassembled, or demounted from the heat sink.

According to other aspects of the present invention, there are providedthe following effects.

(1) The fan guard is provided with a side plate including the shroudsection. The shroud section may be adapted to extend beyond the coolingfan and lie on a more inward side of the heat sink than the position ofthe front end of the fins of the heat sink, so that circumvention of thecooling air can be prevented. Thus, the cooling airflow generated by thecooling fan is fully and smoothly guided toward the heat sink so thatcooling efficiency can be significantly improved.

(2) The fan guard is provided with a side plate including the protrusionsupporting portion. The side plate and the protrusion supporting portionmay be adapted to be sufficient long so as to yield resiliency to theengaging protrusion provided in the protrusion supporting portion, sothat the protrusion supporting portion can be deflected with a smallforce and the engaging protrusion can be easily operated for mountingand demounting. Thus, the fan guard can be quite easily mounted to anddemounted from the heat sink.

(3) Each side surface of the grille section of the fan guard, which isarranged in the circumferential direction of the grille section, may beslanted along the direction of the cooling airflow so that the airresistance or aerodynamic drag of the grille section can be reduced andthe substantial airflow area of the grille section can also beincreased, which results in enhanced cooling efficiency. Further, anyportions protruding toward the cooling airflow can be eliminated so thatno turbulence is generated and wind noise can thereby be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view showing a cooling apparatus forelectrical equipment according to an embodiment of the presentinvention;

FIG. 2 shows the cooling apparatus for electrical equipment according tothe embodiment of the present invention, in which FIG. 2( a) is ahorizontal cross-sectional view of the substantial part thereof, andFIG. 2( b) is an enlarged view of the region A shown in FIG. 2( a);

FIG. 3 is an exploded perspective view showing a conventional coolingapparatus for electrical equipment; and

FIG. 4 shows the conventional cooling apparatus for electricalequipment, in which FIG. 4( a) is a horizontal cross-sectional view ofthe substantial part thereof, and FIG. 4( b) is an enlarged view of theregion B shown in FIG. 4( a).

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1 and 2, an embodiment of the present inventionwill now be described.

FIG. 1 is an exploded perspective view showing a cooling apparatus forelectrical equipment according to an embodiment of the presentinvention. FIG. 2 shows the cooling apparatus for electrical equipmentaccording to the embodiment of the present invention, in which FIG. 2(a) is a horizontal cross-sectional view of the substantial part thereof,and FIG. 2( b) is an enlarged view of the region A shown in FIG. 2( a).

In these drawings, the reference number 1 indicates a heat sink of acontrol unit (not shown) such as an inverter. The heat sink 1 comprisesa gate-shaped frame 4 having a flat section 2, side sections 3 locatedrespectively on both sides of the flat section 2, and fins 5. A fanguard mounting hole 6 is formed respectively in both side sections 3.The frame 4 of the heat sink 1 is equipped with an electronic device(not shown) and thermally connected to a heating member. A cooling fan 7is to be mounted to the frame 4 of the heat sink 1 and has an engaginggroove 8 in each of the side sections of the cooling fan 7. A fan guard9 is to be mounted to the cooling fan 7 so as to cover the front face ofthe cooling fan 7. The fan guard 9 comprises a fan guard body 10 andside plates 11 located respectively on both sides of the fan guard body10, and the fan guard 9 has a gate-like shape. The fan guard body 10 isformed with a grille section 12 for allowing cooling air to passtherethrough. The inner surface of each side plate 11 is provided with afan mounting/engaging protrusion 13 for pressingly clamping andengagingly retaining the cooling fan 7. The outer surface of each sideplate 11 is also provided with a protrusion supporting section 15 havingan engaging protrusion 14 for mounting the fan guard 9 to the heat sink1. The protrusion supporting section 15 has resiliency or flexibility,and includes a tab 16 for releasing the engagement between the fan guard9 and the heat sink 1, at the front end of the protrusion supportingsection 15. The side plates 11 include a shroud section 17 at their rearend portion. When the cooling fan 7 has been assembled or mounted to thefan guard 9, the shroud section 17 has a longer length than that of thecooling fan 7. The number 18 indicates respective mounting screws.

In the cooling apparatus having the above construction, the cooling fan7 and the fan guard 9 are assembled to the heat sink 1 in the followingmanner.

Firstly, the cooling fan 7 is fitted between the side plates 11 byexpanding both side plates of the fan guard 9 outward, and the coolingfan 7 is then mounted to the fan guard 9 by engaging each the fanmounting/engaging protrusions 13 of the side plates 11 with thecorresponding engaging groove 8 of the cooling fan 7 in a snap-inmanner.

Then, the fan guard 9 mounted to the cooling fan 7 is further mounted tothe heat sink 1 in the same snap-in manner. This is achieved byinserting the side plates 11 of the fan guard 9 between both sidesections 3 of the heat sink 1 and by engaging each engaging protrusion14 of the side plates 11 with the corresponding fan guard mounting hole6 formed in the side sections 3 of the heat sink 1.

For maintenance and replacement, the cooling fan 7 is disassembled fromthe heat sink 1 in the following manner.

First, each tab 16 is pushed inward to deflect the protrusion supportingsection 15 inward. This allows each engaging protrusion 14 to be movedinward and be separated from the corresponding fan guard mounting hole6. Thus, the fan guard 9 is demounted from the heat sink 1, stillmounted to the cooling fan 7.

Then, the side sections of the fan guard 3 are respectively openedoutward to move the fan mounting/engaging protrusions 13 outward, sothat the engagement between each fan mounting/engaging protrusion 13 andthe corresponding engaging groove 8 of the cooling fan 7 is released.This allows the cooling fan 7 to be demounted from the fan guard 9.

A cooling apparatus having the above construction achieves its coolingfunction in the following manner.

A cooling airflow is generated by driving the cooling fan 7, and thecooling air flows inside the frame 4 of the heat sink 1. During thisprocess, the shroud section 17 is adapted to extend beyond the coolingfan 7 and lie on a more inward side of the heat sink 1 than the positionof the front end of the fins 5 of the heat sink 1, so that a gap betweenthe cooling fan 7 and the fins 5 of the heat sink 1 is not formed overthe entire surface of the cooling fan 7 in its width direction at theapproximately same position in the longitudinal direction of the coolingfan 7. If some turbulence occurs in the gap, the cooling air is guidedby the shroud sections 17 to flow between fins 5. Thus, the coolingairflow generated by the cooling fan 7 would never be turned over to theinlet side of the cooling fan 7.

The cooling air is introduced from the front end of the heat sink 1,efficiently passed in between fins 5 of the heat sink 1 without anyleakage to outside, and eventually discharged to outside of the controlunit and elsewhere. When the cooling air is passed between the fins 5,heat exchange is performed between the fins 5 and the cooling air sothat the heat sink 1 absorbing the heat of the electronic device andothers (not shown) is reduced in temperature. Thus, the electricaldevice including the control unit is cooled.

As shown in FIG. 2( b), each side surface of the grille section 12 ofthe fan guard 9, which is arranged in the circumferential direction ofthe grille section 12, is slanted along the direction of the coolingairflow so that the air resistance or aerodynamic drag of the grillesection 12 can be reduced and the substantial airflow area of the grillesection 12 can also be increased, which results in enhanced coolingefficiency. Further, any portions protruding into the cooling airflowcan be eliminated so that no turbulence is generated and wind noise canthereby be reduced.

As to mounting and demounting the fan guard 9 to/from the heat sink 1,the fan guard 9 is provided with side plates 11, and the protrusionsupporting portion 15 having a sufficient length is formed respectivelyin side plates 11. Thus, an adequate resiliency or flexibility can beeasily given to the engaging protrusion 14 provided in the protrusionsupporting portion 15 so that the protrusion supporting portion 15 canbe deflected with a small force and the engaging protrusion 14 can beeasily mounted and demounted. Thus, the fan guard 9 can be quite easilymounted to and demounted from the heat sink 1.

In addition, the tab 16 of the protrusion supporting section 15 islocated at the front face of the fan guard 9 so that it can be easilydetermined whether the engaging protrusion 14 is securely engaged bychecking out the position of the tab 16 (If the protrusion 14 is notsecurely engaged, the corresponding tab 16 lies inward.

Furthermore, as needed, when the cooling fan 7 and the fan guard 9 aremounted to the heat sink 1, the screws 18 can screw into threaded holes(not shown) provided in the fan guard 9 to prevent the cooling fan 7 andthe fan guard 9 from falling out, which results in improved safety.

INDUSTRIAL APPLICABILITY

The present invention may apply to a cooling apparatus for electricalequipment, and can be utilized in fields of manufacturing by providing acooling apparatus for electrical equipment which has excellent coolingefficiency and low noise, and which can be easily assembled with acooling fan and fan guard.

1. A cooling apparatus for electrical equipment, comprising: a heat sinkincluding a gate-shaped frame having a flat section and side sectionslocated respectively on both sides of said flat section, fins formed onsaid frame, and a fan guard mounting hole formed in said side section ofsaid frame; a cooling fan having an engaging groove in each side sectionof said cooling fan; and a gate-shaped fan guard including a fan guardbody and side plates located respectively on both sides of said fanguard body, wherein said fan guard body includes a grille section, saidside plates including a shroud section at the rear end portion of eachside plate, said side plates being provided with a fan mounting/engagingprotrusion for clamping and engaging said cooling fan, on the innersurface of said side plate, said side plates including a protrusionsupporting section having an engaging protrusion for mounting said fanguard to said heat sink, in the outer surface of said side plate.
 2. Acooling apparatus for electrical equipment as defined in claim 1,wherein said grille section of said fan guard includes a side surfacearranged in the circumferential direction of said grille section,wherein said side surface is slanted along the direction of a coolingairflow.